Part L (Conservation of Fuel and Power)
The update to the Building regulations includes new insulation requirements for new dwellings, which is now to be assessed under a new Standard Assessment Procedure (SAP) calculation called SAP10.
Self-builders will also have to conduct on-site audits to confirm that the design details in their plans have been constructed, and photographs must be taken as evidence. U-values have also been revised and the recommendations to avoid thermal bridging.
For existing dwellings, minimum new fabric efficiency standards will now apply if you’re looking to introduce new or replacement thermal element to your dwelling, such as new windows, rooflights and doors – meaning a lowering of U-values.
There are new rules for the amount of glazing included in extensions, improvements for lighting design and a new low flow temperature requirement for heating systems. The maximum flow temperature in a central heating system is now 55°C where it was previously over 75°C.

Part F (Ventilation)
The update is intended to make it easier for self-builders and renovators to understand the impact of ventilation dwellings.
It should be noted that when energy efficiency work is done in existing dwellings, the ventilation must not be made any worse, in line with existing measures for controlled services and fittings.
Mandated checklists will now make it easier for installations of mechanical ventilation products – both in new and existing dwellings.
It is now a requirement that replacement windows are provided with trickle vents unless there is an alternative form of background ventilation, such as air bricks or whole house mechanical ventilation with heat recovery or that the works do not result in the ventilation being worse than before the work was carried out.

New Parts to the Building Regulations
Part O (Overheating)
The new Part O is intended to limit excess solar gain in new and existing dwellings and remove excess heat.
Compliance can be achieved through the use of two methodologies with standards based on whether a house is cross-ventilated or not. Also, a standard is included for the maximum amount of glazing allowed in a single room.

Part S (Electric Vehicle Charging)
The new Part S includes the requirement to install charging points for electric vehicles, and provides technical guidance regarding charging them in our dwellings.